In order to obtain direct evidence of the relationship between the structure and acellular milieu of auditory and vestibular receptor cells and the specific response properties of those cells, we are recording intracellularly from primary afferents outside the unopened oti capsule and then injecting diffusible markers for tracing of functionally identified fibers back to their origins at the periphery. During the coming year, we plan to concentrate this effort on two organs of the bullfrog inner ear - the lagena and the amphibian papilla. The work on the lagena will test the hypothesis that striolar receptor cells function differently from peripheral receptor cells in otoconial organs. The work on the amphibian papilla will test definitvely the hypothesis of a place mechanism in frog hearing, shedding light on the evolution of hearing in the anurans and on the mechanism of tone-on-tone inhibition in audition. In parallel with these studies, we plan to continue our morphological research, using SEM in a comparative study of anuran inner-ear structures, and using SEM with cryochamber to examine tectorial and gelatinous membranes in freeze-factured and freeze-etched specimens.